Chiral bilayer dielectric metasurfaces (Conference Presentation)

Chiral photonic metasurfaces were extensively studied because of their ability to act as ultrathin circular polarizers and their potential in chiral sensing [1, 2]. Chiral nanostructures are structures that lack inversion symmetry, i.e., they cannot be mapped onto their mirror image. In nanophotonics, this property allows for a selective interaction with circularly polarized light. The dependence of the optical response of some material on the circular polarization state of the impinging light is called circular dichroism. While huge progress was made in the last decade in creating optical metasurfaces with tailored circular dichroism, the designs realized so far were, with very few exceptions [3, 4], based on plasmonic implementations [5]. However, the large absorption losses in plasmonic devices at optical frequencies often limit their applicability. Here, we study the properties of chiral nanostructures based on high refractive index dielectric materials. In addition to exhibiting low losses, they offer additional opportunities based on multipolar Mie-type response of their building blocks [6]. We experimentally and numerically investigated the zeroth-order transmission spectra of chiral nanostructures consisting of twisted silicon-nanocuboids when illuminated by right and left circularly polarized (RCP and LCP) light. Our experimental and simulated zeroth-order transmission spectra show pronounced difference in the transmission spectra for RCP and LCP light. In conclusion, we have successfully demonstrated an all-dielectric metasurface exhibiting a pronounced chiral optical response. Our results offer important opportunities for high-efficiency circular polarizing elements. [1] Gansel, J. K. et al., M. Science 2009, 325,1513−1515. [2] Zhao, Y. et al., Nat. Commun. 2016, 8, 1−8. [3]Zhu. A. et al., Light: Science & Applications 2018, 7, 17158. [4]Ma. Z. et al., Opt. Express 2018, 26, 6067-6078. [5] Decker, M. et al., Opt. Lett. 2009, 34, 2501−2503. [6] Staude, I. and Schilling, J., Nature Photonics, 2017, 11, 274-284.